Recent progress in the development of a polarized proton target for reactions with radioactive ion beams

Polarization observables in nuclear reactions with stable beams have provided important information concerning structural properties of nuclei and reaction mechanisms and hold great promise in the context of exotic nuclei. We report on the development of a polarized target based on plastic foils of 20-200 mu m thickness to be used with radioactive ion beams. The operation of such a target requires a moderately high magnetic field and very low temperatures. The plastic foil is placed inside a chamber attached to the mixing chamber of a He-3-He-4 dilution refrigerator. Cooling of the foil is achieved via a superfluid film of He-4 that can be supplied through two capillaries. The chamber has two thin, highly uniform silicon nitride windows. An NMR coil is attached to the target to monitor the polarization. Results of a first test to characterize the target system, using the elastic scattering of 38 MeV C-12 by protons in inverse kinematics are presented. (c) 2007 Elsevier B.V. All rights reserved.